This invention relates to free-standing crystalline boron phosphide films, and to a method for preparation thereof.
Boron phosphide is desirable for use in device applications. More specifically, boron phosphide has already shown promise as a conductive anticorrosive coating. However, although boron phosphide's value as a semiconducting material has been appreciated, its full potential has not been developed because of difficulties encountered in obtaining free-standing material. Preparation of a free-standing crystalline film of boron phosphide would enable studies to be conducted to electrically characterize the material, as well as permitting device fabrication therewith.
The prior art processes for producing crystalline boron phosphide have all failed to achieve production of a free-standing film capable of use in many device applications. For instance, U.S. Pat. No. 2,966,426 teaches a process for forming boron phosphide, but only as a coating, or as a crushed material removed from the walls of a production chamber. This patent fails to teach the use of boron phosphide (hereinafter BP, as opposed to other boron phosphides such as B.sub.6 P, B.sub.20 P, B.sub.70 P or B.sub.100 P, etc.) in electronic device applications.
U.S. Pat. No. 3,363,984 teaches a process wherein boron phosphide is produced in a hot tube reactor and thereafter scraped off the walls for use as an abrasive. U.S. Pat. No. 3,260,571 teaches production of B.sub.6 P particles for use in semiconductor applications and U.S. Pat. No. 3,340,009 teaches production of monocrystals, as well as polycrystals of BP for use in electronic semiconductors. The crystalline BP of U.S. Pat. No. 3,340,009 is not in free-standing film form.
U.S. Pat. No. 3,395,986 teaches production of BP as a dispersed component in a solidified salt matrix. U.S. Pat. No. 3,357,795 teaches growth of BP crystals on the walls of a chamber and U.S. Pat. No. 3,279,891 teaches production of fine-crystalline BP.
However, none of the above-discussed references teaches a process for production of a free-standing film of highly pure BP.